In my fermentation bucket, a thick brown sludge has built up around the edges of the bucket. It was not there 4 hours ago. The brew itself looks perfectly golden, bubbly and normal, but the sludge is worrying. Is this common? Thanks

edit: Upon further inspection it appears to be the residue from the initial bubbles... can anyone shed some light on the subject?

+1 to peterfuse. I'm assuming this is your first batch? Kraussen is a part of every brew. Some can look beautiful like a creamy frothy head on a pint, others, and most, will look quite gross. It will fall.

The fermentation activity causes the volume of the wort to expand, so you will often see a brown crusty ring an inch or more above the level of your wort. That's because the krausen rose, deposited that ring, then sank back down. It's actually called "high krausen" at that point. Kinda like the ring around the bathtub.